The invention relates to turbine engine blades having internal channels.
In order to reduce noise and turbulence at the root of a blade, it is known to make internal channels within blades, which channels open out in the vicinities of the root and of the tip of the blade. These internal channels thus form a suck/blow device that draws in (sucks) some of the air level with the root of the blade and exhausts it (blows it out) level with the tip of the blade, thereby enabling a portion of the boundary layer in the proximity of the rotor to be absorbed.
Such blades provided with such suck/blow devices are generally made of a metal material, with the internal channels being hollowed out in the mass of the blade.
Nevertheless, machining internal channels in blades of metal material is quite difficult and can only be done on blades presenting shapes that are relatively simple. In particular, it is not possible to machine internal channels in metal blades that present a twisted shape.
In order to obtain blades of lighter weight, it is known to make blades out of composite material, i.e. by making parts of a structure that comprises fiber reinforcement densified by a matrix.
The technique that is generally used consists in forming a stack of pre-impregnated unidirectional sheets or plies (draping) that are placed in a mold with the successive plies being oriented in different directions, prior to compacting and polymerizing in an autoclave.
In another technique that is more recent and that provides better performance, the blade is fabricated by three-dimensionally weaving a fiber preform and then densifying the preform with a matrix. Document EP 1 526 285 describes a method of fabricating such a blade.
Nevertheless, known blades of composite material do not include internal channels. Machining internal channels in a blade of composite material can spoil the properties and the strength of the blade. Drilling one or more channels may in particular lead to certain reinforcing yarns being damaged or even broken, thereby harming the cohesion of the fiber reinforcement (by interrupting the paths along which forces are transmitted, which paths are formed by the reinforcing yarns).
Nevertheless, composite material blades represent a solution for the future, in particular because of their light weight and because of their excellent mechanical properties.